The present invention relates to a network system for transmitting data between terminating nodes through an Asynchronous Transmission Mode (ATM) switch network. More particularly, the present invention relates to a transmission apparatus provided between a terminating node and an ATM switch network to resolve an ATM address.
As systems for connecting an existing (Local Area Network) (LAN) and an ATM switch, a LAN-emulation system and an Internet Protocal (IP) over-ATM system are available. The LAN-emulation system emulates an existing LAN such as the Ethernet and a token link to convert a MAC address on the existing LAN into an ATM address. The IP-over-ATM system is a system for converting an IP address on an IP network into an ATM address. The LAN-emulation system is described in xe2x80x9cATM-Switch Network Bible with Explanatory Diagramsxe2x80x9d Ohm Corporation pg. 111-115. As for the IP-over-ATM system, such is described in Requests for Comments (RFC) 1577 and RFC 1755 by the Internet Engineering Task Force (IETF).
FIG. 18 is an explanatory diagram used for describing a technique adopted by the LAN-emulation system for resolving an address. As shown in FIG. 18, an ATM-switch network is connected to a variety of apparatuses including LECs LAN emulation clients (LECs) denoted by notations LEC-A, LEC-B and LEC-C in FIG. 18, an LECS (LAN emulation configuration server), a LAN emulation server (LECS) and a broadcast and unknown server (BUS). The LECS, LES and BUS are each a server for rendering services of resolving addresses. The LEC has an interface with an existing LAN and an ATM interface. Provided between an existing LAN and an ATM-switch network, the LEC is an apparatus playing the role of a bridge between the networks. An LEC composes an existing LAN in conjunction with terminating nodes.
LEC-A, an ATM end apparatus, acquires an ATM address of LEC-B by following a procedure described as follows. At step (1), in an initialization which is carried out when the power supply is turned on, LEC-A establishes a logical connection with the LECS for controlling the ATM address of the LES in order to acquire the ATM address of the LES. The LES controls an address control table, that is, a table associating the MAC address of each LEC with a corresponding ATM address. At step (2), when LEC-A receives a frame from a terminating node, LEC-A establishes a logical connection with the LES by using the ATM address of the LES acquired at step (1) to send the LES an inquiry about an ATM address of LEC-B, the data-transfer destination of the frame, on the basis of a destination MAC address of LEC-B described in the frame. If an ATM address of LEC-B associated with the MAC address of LEC-B is cataloged in the address control table in the LES, the LES transmits the ATM address of LEC-B in response to the inquiry at step (3). If an ATM address of LEC-B associated with the MAC address of LEC-B is not cataloged in the address control table of the LES, on the other hand, the LES sends the BUS an inquiry about the ATM address. Receiving this inquiry, the BUS sends all TECs connected to the ATM-switch network an inquiry about their ATM addresses by using a broadcasting technique at step (4). The BUS then transmits the ATM address of TEC-B obtained as a result of the broadcasted inquiry to the LES. Then, the LES catalogs the ATM address in the address control table, associating the ATM address with the MAC address of LEC-B. Subsequently, the LES transmits the ATM address of LEC-B to LEC-A. At step (5), LEC-A establishes a logical connection with LEC-B by using the received ATM address. LEC-A then generates cells from the frame received from the terminating node, transmitting the cells to LEC-B.
FIG. 19 is an explanatory diagram used for describing a technique adopted by the IP-over-ATM system to resolve an address. As shown in FIG. 19, the ATM-switch network is provided with an ATM-ARP (Address Resolution Protocol) server. Introduced between an existing LAN and the ATM-switch network, an ATM client plays the role of a router. ATM clients, namely, ATM clients A and B in the case of an example shown in FIG. 19, each compose an existing LAN in conjunction with terminating nodes.
ATM client A, an ATM end apparatus, acquires an ATM address of ATM client B by following a procedure described as follows. At step (1), in an initialization which is carried out when the power supply is turned on, ATM clients A and B each establish a logical connection with the ATM-ARP server. At that time, the ATM-ARP server sends ATM clients A and B an inquiry about their IP addresses and, in response to the inquiry, ATM clients A and B transmit their IP addresses to the ATM-ARP server. The ATM-ARP server creates an address control table, that is, a table associating an IP address of each ATM client with a corresponding ATM address. At step (2), when ATM client A receives a frame from a terminating node, ATM client A sends the ATM-ARP server an inquiry about an ATM address of ATM client B, the data-transfer destination of the frame, on the basis of a destination IP address of ATM client B described in the frame. At step (3), the ATM-ARP server searches the address control table for an ATM address of ATM client B with the IP address used as a key, transmitting the ATM address to ATM client A. At step (4), ATM client A establishes a logical connection with ATM client B by using the received ATM address. ATM client A then generates cells from the frame received from the terminating node, transmitting the cells to ATM client B.
As described above, in the LAN-emulation system, servers such as the LECS, the LES and the BUS are required in order to resolve an ATM address. In the case of the IP-over-ATM system, on the other hand, the ATM-ARP server is needed. In addition, when a failure occurs in one of these servers, an ATM address can not be resolved, giving rise to a problem that communications among ATM end apparatuses can not be carried out. Moreover, in order to resolve an ATM address, accesses are concentrated on a server, raising a problem of a long response time. Further, an ATM client of the IP-over-ATM system can not help carrying out processing by software due to intervention of communication with a server at a so-called Internet layer in the TCP/IP protocol system. As a result, the performance deteriorates due to an overhead entailed by the processing by software.
An object of the present invention is to provide an ATM apparatus which resolves an ATM address without using a server.
The present invention is a transmission apparatus which resolves an ATM address. The transmission apparatus is provided between a terminating node and an ATM-switch network. The transmission apparatus includes a first apparatus which receives an ATM address of another transmission apparatus and a layer-3 address of a terminating node connected to the other transmission apparatus from the other transmission apparatus, and catalogs the ATM address and the layer-3 address into a table; and a record apparatus which searches the table using a layer-3 address of a destination terminating node which is a destination of transmission of data received from a source terminating node connected to the transmission apparatus to acquire an ATM address of the other transmission apparatus connected to the destination terminating node, and communicates with the other transmission apparatus by using the acquired ATM address to transmit a cell including information of the layer-3 address of the destination terminating node.
In addition, the present invention provides a network system including the above described transmission apparatus. Terminating nodes and transmission apparatuses constitute a network like an existing LAN wherein communication is carried out by using a layer-2 address. The transmission apparatuses form an ATM-switch network, wherein communication is carried out by using an ATM address. Terminating nodes compose a network like an IP network wherein communication is carried out by using a layer-3 address.